Kieu Gioseffi

I am interested in buying a Property in Ambattur chennai. The total plot size is 6000 Sq Ft and i want to buy 3000 Sq Ft. The Property is a Grama nattham property. The seller has SLR patta for the land. In the SLR Patta there are three owners a Lady and her two sons. The lady has expired and now her sons are selling the property. The Lady also has 2 daughters and there is no documentation in their names. I spoke with the sellers about this and they told that when their mother died they had a settlement and paid thier sisters with gold and money as wished by their mother. I have Encumbrance Certificates from 1971 to 1987 (Manual ) and 1987 to 2012 (Computerized ) and it is Nil certificate of encumberance on the above mentioned property. I enquired in the area and found that the sellers have been living there for many years and all their neighbours know them very well. They do not have a legal heir certificate , but i have asked for it and they have applied for it now. When i enquired about the Legal heir certificate many told me that it is not of much importance if you do not have any litigations against the property. My questions are as follows : 1. Based on the above information mentioned do you think i have all the required information about the property , if not what other information i need to collect ? 2. If in case i am buying this property, do i need the approval from the daughters and their signature in the sale deed ? 3. The SLR Patta has been issued by the Tahsildar, is this a valid document ? 4. I also have a copy of a registered document dated 1918 when this land was bought by the sellers Great grand mother. Is this now valid ?